Method and apparatus of treating ingots of iron or steel



R. RINESCH May 14, 1963 METHOD AND APPARATUS OF TREATING INGOTS OF IRONOR STEEL Filed April 2'7. 1960 JNVENTOR.

RU DOLF RI NESCH HIS ATTORNEYS atet 3,089,767 Patented May 14, 19633,089,767 METHOD AND APPARATUS OF TREATING INGOTS OF IRON OR STEELRudolf Rinesch, Linz (Danube), Austria, assignor to VereinigteOsterreichische Eisenund Stahlwerke Aktiengesellschaft, Linz, Austria, acompany of Austria Filed Apr. 27, 1960, Ser. No. 24,941 Claims priority,application Austria Apr. 30, 1959 e 2 Claims. (Cl. 7551) This inventionrelates to a method of treating ingots of iron or steel, particularly ofsteel ingots having a weight of more than 8 metric tons, and has as itsobject to avoid or minimize segregation.

In the casting of steel ingots of large size, particularly of ingotshaving a weight exceeding 8 metric tons, segregation occurs, which isdetrimental. The segregation is caused by the content of alloyingelements such as sulphur, phosphorus and carbon in the steel. The pouredsteel begins to solidify from the bottom and the Walls of the ingotmould. The portions solidifying first have the smallest content ofalloying elements whereas the portion which has remained liquid in thephases of the solidification is progressively enriched. The severalalloying elements are subject to this tendency in different degrees.Sulphur and phosphorus have a greater tendency to segregate than carbon.The segregation results in deviations from the as-teemed analysis sothat the proportion of alloying elements in the molten metal in the topcentral portion of the ingot may be a multiple of the desired orpermissible values. In that case the head of the ingot is not suitablefor the intended use and must be processed as scrap.

It is an object of the invention to eliminate these difiiculties. Theinvention resides in re-refining the teemed block by blowing with oxygenor with a high-oxygen gaseous refining agent as soon as its centrebegins to become pasty and simultaneously adding basic slag-formingsubstance such as lime dust and calcined sodium carbonate. The oxygenjet is suitably blown in a vertical direction onto the central region ofthe surface of the pasty upper portion of the block and the basicslagforming substances are blown in finely divided suspended formtogether with the oxygen. In this way the surplus content of thealloying elements is quickly removed.

The removal of the segregation promoting elements by means of thetreatment according to the invention can be checked by intermediatetests. In a preferred procedure the re-refining is carried out untilvalues have been reached which are somewhat lower than those of thedesired analysis, whereafter the treatment is discontinued. As thesolidification of the ingot continues the segregation of the ingot isresumed and makes up for the deficiency of the removed alloyingelements. The desired values will then be obtained when thesolidification has been completed.

15-ton ingots of rimming steel have been treated according to theinvention. In the following table the carbon, phosphorus and sulphurvalues in treated ingots are compared with the corresponding values inuntreated ingots. In order to show the influence of segregation independence on the progress of the solidification the samples have beentaken at varying distances from the head of the ingot. Charges 1 to 3were re-refined (treated) with oxygen and lime dust. This indicatesparticularly the influence, of the treatment on the phosphorus content.Charges 4 and 5 Were re-refined (treated) with oxygen to which a mixtureof lime dust and calcined sodium carbonate was added. This shows theinfluence of the treatment on the phosphorus and sulphur contents.

TREATMENT BY BLOWING OXYGEN AND FINELY I DIVIDED LIME DUST [Weight ofingot 15 metric tons] 0 Mn P S Charge 1:

Analysis as teemed 0.08 0.38 0.018 0.027 Ingot I (treated)- Sample(a)Distance from head 6% 0.06 0.020 0.043 Sample (b)Distauce from head57% 0.10 0.014 0.032 Iugot II (untreated) Sample (a)Distance from he d6%0.13 0.032 0.046 Sample (b)Distance from head 57% 0.09 0.025 0.034Charge 2:

Analysis as teemed 0.09 0.45 0.019 0.024 Ingot I (treated)- Sample(a)Distance from 0.14 0.025 0.030 Ingot II (untreated)-- Sample(a)-Distance from head6 a 0.12 0.033 0.058 Sample (b)Distance from head16% 0.26 0.055 0.102 Charge 3:

Analysis as teemed 0.12 0.35 0.015 0.022 Ingot I (treated) Sample(a)Distance from head 0.10 0.019 0.045 Sample (b)Distance from head 16%0.14 0.022 0.064 Ingot II (untreated) Sample (a)Distance from head 6%0.27 0.037 0.125 Sample (b)-Distance from head 16% 0.32 0.039 0.126

TREATMENT BY BLOWING OXYGEN AND A MIXTURE OF LIME DUST AND FINELYDIVIDED CALOINED SODIUM CARBONATE [Weight 01 ingot 15 metric tons] 0 MnP S Charges 4:

Analysis as refined 0.10 0.42 0.018 0.025 Ingot I (treated)- Sample(a)-Distance from head 6% 0.07 0.016 0.017 Sample (b)Distance from head16 a 0.15 0.026 0.031 Ingot II (untreated) Sample (a)Distance from head5% 0.19 0.032 0.067 Sample (b)Distance from head 17% 0.21 0.046 0. 073Charge 5:

Analysis as teemed 0.14 0.39 0.020 0.023 lngot I (treated)- Sample(a)Distance from head 6% 0.11 0.023 0.018 Sample (0)Distance from head15% 0.18 0.031 0.027 Ingot II-(untreated) Sample (a)Distanee from head77 0. 20 0. 029 0. 051 Sample (12) head 16% 0.19 0.048 0.068

Apparatus which can be used to advantage for carrying out the methodaccording to the invention is diagrammatically shown on the accompanyingdrawing.

The main parts of this apparatus comprise a supply conduit 1 for oxygenor a high-oxygen gaseous refining agent, a pressurized supply container2 for finely divided basic substances 3, an injector 4 and a blowingtube 5. By means of a regulating valve 6 a pressure of, e.g., 10 kg./sq. cm. superatmospheric pressure is adjusted in the supply conduit 1.The conduit 1 is connected by a branch conduit 7 to the top part of thesupply container 2. By means of the regulating valve 8 the same internalpressure as in conduit 1, e.g., 10 l g./sq. cm. superatmosphericpressure, is maintained in the container 2. The conduit 1 is continuedby a regulating valve 9 and a conduit section 10 connected to theinjector 4. This portion of the conduit is maintained at a lowerpressure than the supply container. The pressure may be approximately 6kg./sq. cm. superatmospheric pressure. The injector comprises aconcentric tube 11, which surrounds the conduit tube 10 and which tapersat the tip 12. The inner tube 10 is fitted in the outer tube 11 by meansof the stufling box 20 and is axially slidable therein. By means of aconnecting pipe 13 the tube 11 communicates with the tapered bottom 14of the supply container. This connecting pipe may incorporate a controlcock 15. Owing to the higher pressure in the supply container the finelydivided substances, lime dust and calcined sodium carbonate, are forcedthrough the connecting pipe 13 into the tip 12 of the shell tube 11 andare entrained there by the oxygen jet. The front end 12 of the tube 11is connected by the conduit portion 16 to the blowing tube 5. Theblowing tube is centrally and vertically disposed over the ingotcontained in the ingot mould 17. The upper part of the ingot mould maybe lined with an annular insert 18 of sheet metal or refractorymaterial.

What I claim is:

1. A method of treating ingots of a metal of the class consisting ofiron and steel comprising pouring the molten metal into an ingot mold,cooling the metal to form a solidified outer portion and form a pastycentral region in the upper portion of the ingot in the mold, thenblowing a jet of high-oxygen gas having finely-divided basicslag-forming agents comprising lime and calcined sodium carbonatesuspended therein against the pasty central region of the ingot andcontinuing blowing until phosphorus and sulfur in said central regionare reduced to not substantially in excess of their desired finalcontent in the ingot, and terminating blowing to enable segregation ofthe sulfur and phosphorus to continue in said central region of theingot.

2. The method set forth in claim 1 in which blowing is continued untilphosphorus and sulfur in the upper region ofthe ingot are reduced toless than their desired final content in the ingot.

References Cited in the file of this patent UNITED STATES PATENTS2,236,504 Herty Apr. 1, 1941 2,892,699 Austin et al June 30, 19592,906,617 Wahl Sept. 29, 1959

1. A METHOD OF TREATING INGOTS OF A METAL OF THE CLASS CONSISTING OFIRON AND STEEL COMPRISING POURING THE MOLTEN METAL INTO AN INGOT MOLD,COOLING THE METAL TO FORM A SOLIDIFIED OUTER PORTION AND FORM A PASTYCENTRAL REGION IN THE UPPER PORTION OF THE INGOT IN THE MOLD, THENBLOWING A JET OF HIGH-OXYGEN GAS HAVING FINELY-DIVIDED BASICSLAG-FORMING AGENTS COMPRISING LIME AND CALCINED SODIUM CARBONATESUSPENDED THEREIN AGAINST THE PASTY CENTRAL REGION OF THE INGOT ANDCONTINUING BLOWING UNTIL PHOSPHORUS AND SULFUR IN SAID CENTRAL REGIONARE REDUCED TO NOT SUBSTANTIALLY IN EXCESS OF THEIR DESIRED FINALCONTENT IN THE INGOT, AND TERMINATING BLOWING TO ENABLE SEGREGATION OFTHE SULFUR AND PHOSPHORUS TO CONTINUE IN SAID CENTRAL REGION OF THEINGOT.